[PATCH] D78234: [BranchFolding] assert when removing INLINEASM_BR indirect targets

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers updated this revision to Diff 258154.
nickdesaulniers marked 6 inline comments as done.
nickdesaulniers added a comment.
Herald added a subscriber: MatzeB.

- delete transferInlineAsmBrIndirectTargets so that we can use isInlineAsmBrIndirectTarget correctly.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D78234/new/

https://reviews.llvm.org/D78234

Files:
  llvm/include/llvm/CodeGen/MachineBasicBlock.h
  llvm/lib/CodeGen/BranchFolding.cpp
  llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp


Index: llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -1072,8 +1072,6 @@
     CopyBB->normalizeSuccProbs();
     BB->normalizeSuccProbs();
 
-    BB->transferInlineAsmBrIndirectTargets(CopyBB);
-
     InsertPos = CopyBB->end();
     return CopyBB;
   }
Index: llvm/lib/CodeGen/BranchFolding.cpp
===================================================================
--- llvm/lib/CodeGen/BranchFolding.cpp
+++ llvm/lib/CodeGen/BranchFolding.cpp
@@ -159,6 +159,25 @@
 void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) {
   assert(MBB->pred_empty() && "MBB must be dead!");
   LLVM_DEBUG(dbgs() << "\nRemoving MBB: " << *MBB);
+#ifndef NDEBUG
+  if (MBB->hasAddressTaken())
+    for (const MachineBasicBlock &Pred : *MBB->getParent())
+      // Iterating Pred.terminators() may be unreliable in this case.
+      // MachineBasicBlock#getFirstTerminator() iterates backwards through the
+      // MachineBasicBlock's MachineInstrs to the first non-Terminal, then
+      // moves forward one and returns that. If a non-terminator gets inserted
+      // after the INLINEASM_BR, perhaps by accident, then
+      // MachineBasicBlock#getFirstTerminator() and
+      // MachineBasicBlock#terminators() will not return the INLINEASM_BR
+      // terminator.
+      for (const MachineInstr &I : Pred)
+        if (I.getOpcode() == TargetOpcode::INLINEASM_BR)
+          for (const MachineOperand &Op : I.operands())
+            if (Op.isBlockAddress() && Pred.isInlineAsmBrIndirectTarget(MBB) &&
+                Op.getBlockAddress()->getBasicBlock() == MBB->getBasicBlock())
+              llvm_unreachable(
+                  "Removing MBB that's an indirect target of INLINEASM_BR");
+#endif
 
   MachineFunction *MF = MBB->getParent();
   // drop all successors.
Index: llvm/include/llvm/CodeGen/MachineBasicBlock.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -484,13 +484,6 @@
     InlineAsmBrIndirectTargets.insert(Tgt);
   }
 
-  /// Transfers indirect targets to INLINEASM_BR's copy block.
-  void transferInlineAsmBrIndirectTargets(MachineBasicBlock *CopyBB) {
-    for (auto *Target : InlineAsmBrIndirectTargets)
-      CopyBB->addInlineAsmBrIndirectTarget(Target);
-    return InlineAsmBrIndirectTargets.clear();
-  }
-
   /// Returns true if this is the default dest of an INLINEASM_BR.
   bool isInlineAsmBrDefaultTarget() const {
     return InlineAsmBrDefaultTarget;


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